Telescopic extension jibs for crane booms have been employed in the prior art but have not been completely practical because of the extreme difficulty of manual manipulation of the movable jib section. Most construction cranes have no more than two operators and many have only a single operator. It is extremely difficult, if not impossible, for one operator or even two to extend the interior movable section of a telescopic jib due to the massiveness of the same and the high friction forces which resist manual manipulation. In some instances, crane operators have resorted to unusual procedures such as securing the movable section of the jib to some fixed structure and backing up the crane to extend the jib. This is highly inconvenient and could result in damage to the jib or other parts of the crane and the procedure is not advisable.
Accordingly, the objective of this invention is to provide a telescopic extension jib for crane booms which can easily be extended and retracted manually by one operator and is therefore completely practical and convenient to use. The extension jib increases the reach of the crane boom and thus increases the overall utility of the crane in comparison to cranes having nontelescopic extension jibs.